Pacific earthquake: An 8.0 Pacific earthquake hit about 1,000 miles northeast of Australia. Over the past half-century, three 9.0 or higher 'superquakes' have hit the Pacific's Ring of Fire, pushing scientists to rethink their models of earthquake formation.

The 8.0 Pacific quake that hit the Solomon Islands tonight should be about most powerful earthquake possible, according to seismologists' theories of earthquake cycles. And the earthquakes that rocked Tohoku, Japan in 2011, Sumatra in 2004, and Chile in 1960 — all of magnitude 9.0 or greater — should not have happened. That might mean earthquake prediction needs an overhaul, some researchers say.

All these earthquakes struck along subduction zones, where two of Earth's tectonic plates collide and one dives beneath the other. Earlier earthquakes had released the pent-up strain along Chile's master fault, meaning no big quakes were coming, scientists had thought. Japan and Sumatra both sat above on old oceanic crust, thought to be too stiff for superquakes.

And records of past quakes, combined with measurements of the speed of Earth's tectonic plates, suggested the Tohoku and Sumatra-Andaman regions couldn't make quakes larger than 8.4, almost nine times smaller than a magnitude 9.0 temblor.

"These areas had been written off as places incapable of producing a great earthquake," said Chris Goldfinger, a marine geologist at Oregon State University in Corvallis.